In fully automated motor vehicles the driver is no longer engaged in the task of driving. This increases the requirements on vehicle systems, in particular the vehicle sensory systems. Most vehicles sensory systems relied on today have capabilities which decrease with increased sensing distances. This presents a challenge as the sensors of the sensory systems are required to detect any objects present in the future path of the vehicle, while at the same time minimizing the number of false or erroneous detections.
Today's sensor systems have good object classification capabilities at short and medium ranges, e.g. below 50 m. This is especially achieved by having fused information between different sensors, e.g. radar sensors and camera based sensors.
However, at longer ranges the capability to discern threatening objects from irrelevant or erroneous object reflections, e.g. sensing ghosts, decreases dramatically.
One attempt to ensure that an automatic traveling vehicle with an object detector can travel at high speed without colliding or interfering with a detected object is described by U.S. Pat. No. 6,347,266.
The vehicle described by U.S. Pat. No. 6,347,266 is controlled in accordance with a method to travel along a predetermined course, information representative of which is provided. Objects in a path of the vehicle are detected by transmitting a medium in a direction and evaluating the medium reflected from any objects in the direction.
An object detector receives reception and transmission information, i.e. in other words, a frequency, a reception and transmission strength, and the like, regarding the directional medium produced and received. An object detector further analyzes an object detection status, i.e. whether or not any object is detected, a distance to an object, a relative speed to an object and the like.
The direction to transmit the medium is determined based on at least the information representative of the predetermined course. A current vehicle speed is adjusted based on detected objects. A critical detection area, representative of an actual area defined by the medium radiated through a predetermined angular range, is determined.
The step of determining the direction to transmit the medium is further based on the critical detection area. The step of adjusting current vehicle speed includes determining a current position of the vehicle relative to the predetermined course, and providing a plurality of predetermined speed settings, where each predetermined speed setting corresponds to a braking distance. A current speed of the vehicle is determined as well as a farthest distance from the current position of the vehicle in an area defined by overlapping the critical detection area with the predefined course.
Thus, the current vehicle speed is adjusted to a speed not to exceed a predefined speed setting having a corresponding braking distance equal to the farthest distance. According to the above configuration, the automatic traveling vehicle is capable of evaluating the greatest effective detection area. Thus, the automatic traveling vehicle can travel at high speed without colliding or interfering with a detected object.
However, the vehicle described by U.S. Pat. No. 6,347,266 will thus always adapt it speed such that it is able to perform braking action if an object is detected within the greatest effective detection area.
Known systems of the above described type will, in order to minimize false detection, usually perform speed adaptation first once the object detector is convinced that an object is detected. This may lead to an automated speed reduction or braking being performed quite late and therefore possibly also quite hard. As a consequence thereof, in order to ensure good long range performance, more sophisticated and therefore usually also more expensive sensors may be relied on, which increases system cost and complexity.